JPS5827071A - Photomagnetic field detector - Google Patents
Photomagnetic field detectorInfo
- Publication number
- JPS5827071A JPS5827071A JP12518381A JP12518381A JPS5827071A JP S5827071 A JPS5827071 A JP S5827071A JP 12518381 A JP12518381 A JP 12518381A JP 12518381 A JP12518381 A JP 12518381A JP S5827071 A JPS5827071 A JP S5827071A
- Authority
- JP
- Japan
- Prior art keywords
- magnetic field
- light
- prism
- optical fiber
- optical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
- G01R33/0322—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect using the Faraday or Voigt effect
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Measuring Magnetic Variables (AREA)
Abstract
Description
【発明の詳細な説明】
本発明は、光ファイバと光の偏波面の回転能（ファラデ
ー回転能）を利用した磁界測定装置において、磁界以外
の外乱（例えば、光ファイバの曲げによる光損失、温度
変化による光透過事変化）にも安定な磁界検出を可能と
する方法−関する。DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic field measuring device that utilizes an optical fiber and its ability to rotate the polarization plane of light (Faraday rotation ability), which is capable of detecting disturbances other than magnetic fields (for example, optical loss due to bending of an optical fiber, temperature The present invention relates to a method that enables stable magnetic field detection even when light transmission changes (changes in light transmission due to changes).
従来、光ファイバとファラデー回転能をもつ素子を組合
せた磁界検出方法は第１図に示す構成を取っていた。光
源１からの無偏光の光を光ファイバ２−１で磁界検出部
人に導く。磁界検出部人は偏光子３、ファラデー回転素
子４、検光子５よりなり、光ファイバ２−１の無偏光の
光は偏光子３で直線偏光成分が取り出されファラデー回
転素子４に注入される。ファラデー回転素子４は、光の
進行方向に印加された磁界の強さＨに比例しただけ直線
偏光の光を、面内で回転させる。検光子５は通常偏光子
３と４５°の角度で相対しており、ファラデー回転素子
４による直線偏光の回転で検光子５ｔ−通る光の強度が
変化する。この光を光ファイバ２−２で光検出器６まで
導き、出力を検出する。この検出出力は磁界の強さＨに
比例して次のように書きあられせる。Conventionally, a magnetic field detection method that combines an optical fiber and an element with Faraday rotation ability has had the configuration shown in FIG. Unpolarized light from a light source 1 is guided to a magnetic field detection unit through an optical fiber 2-1. The magnetic field detection unit is composed of a polarizer 3, a Faraday rotation element 4, and an analyzer 5. A linearly polarized component of unpolarized light from the optical fiber 2-1 is extracted by the polarizer 3 and is injected into the Faraday rotation element 4. The Faraday rotation element 4 rotates linearly polarized light within a plane in proportion to the strength H of the magnetic field applied in the direction in which the light travels. The analyzer 5 normally faces the polarizer 3 at an angle of 45 degrees, and the rotation of the linearly polarized light by the Faraday rotation element 4 changes the intensity of the light passing through the analyzer 5t. This light is guided to a photodetector 6 through an optical fiber 2-2, and the output is detected. This detection output is proportional to the magnetic field strength H and can be written as follows.
Ｐｏｏｔ＝ｋＰｏ （１−８ｉｎ２Ｆ）／２ ・凹曲・
＝・（１）ここで Ｐｏｕｔ：検出出力
Ｐｏ：光源の光の強さ
ｋ ：伝送効率
Ｆ ：ファラデー回転角
ファラデー回転角は通常次式であられされる。Poot=kPo (1-8in2F)/2 ・Concave curve・
=・(1) where Pout: Detection output Po: Light intensity k of the light source: Transmission efficiency F: Faraday rotation angle The Faraday rotation angle is usually expressed by the following equation.
Ｆ＝Ｖ、ＨＬ ・・・・・曲曲曲・曲曲曲・四囲〇）
■、：ベルデ定数
Ｌ ：ファラデー素子の長さ
ベルデ定数Ｖ、はファラデー回転素子固有の定数である
。F=V, HL...muscles, melodies, squares 〇)
(2): Verdet constant L: Length of Faraday element Verdet constant V is a constant specific to the Faraday rotation element.
式（１）における伝送効率には、光ファイバの伝送損失
、光源から光ファイ、バへの光の注入率、光フアイバ端
面の反射率、ファラデー回転素子の光の吸収損失、偏光
子の透過率などに関するものである。第１図に示した磁
界検出器が完全に理想的な場合には式（１）、（２）よ
り出力は磁界の強さＨのみによって変化し、その出力よ
り逆に磁界の強さＨが求められる。しかし一般に光源１
がらの光の強さＰａは時間的に、また外部温度変動によ
って変化する。マえ、光ファイバから偏光子３を介して
フも
アラデー回転素子４に入る直線偏その光の強さも変化す
る。これは光ファイバ２−１内の光の偏光状態がつねに
完全にランダムな無偏光でないからである。このため、
弐〇）の伝送効率にも時間的に変化する。このため、磁
界検出が不安定になり、最小検出磁界が上記ノイズによ
って決定される。The transmission efficiency in equation (1) includes the transmission loss of the optical fiber, the injection rate of light from the light source to the optical fiber, the reflectance of the optical fiber end face, the light absorption loss of the Faraday rotator, and the transmittance of the polarizer. etc. If the magnetic field detector shown in Figure 1 is completely ideal, the output will change only depending on the magnetic field strength H from equations (1) and (2); Desired. However, generally light source 1
The intensity of the light Pa changes over time and due to external temperature fluctuations. Furthermore, the intensity of the linearly polarized light that enters the Alladay rotation element 4 from the optical fiber via the polarizer 3 also changes. This is because the polarization state of the light within the optical fiber 2-1 is not always completely random and non-polarized. For this reason,
The transmission efficiency of 2〇) also changes over time. Therefore, magnetic field detection becomes unstable, and the minimum detected magnetic field is determined by the noise.
本発明の目的は磁界以外の外乱（例えば光源の変動、光
ファイバの伝送損失変動）によっては出力が安定な磁界
検出方法を提供することにある。SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic field detection method whose output is stable despite disturbances other than magnetic fields (for example, fluctuations in a light source and fluctuations in transmission loss of an optical fiber).
以下、本発明を図を用いて詳細に説明する。第２図は本
発明における磁界検出器の構成図である。Hereinafter, the present invention will be explained in detail using the drawings. FIG. 2 is a configuration diagram of a magnetic field detector according to the present invention.
磁界検出部Ａは偏光子３、ファラデー回転素子４、光学
プリズム７よりなり、偏光子３の光の振動方向（直線偏
光の向き）と光学プリズムの光主軸かのを用い、光ファ
イバ２−２を介してそれぞれを光検出器６−１．６−２
で検出する。ここで光学プリズムは検出される光の強さ
Ｐ＋、Ｐａがそれぞれ次式であられされるものをもちい
る。The magnetic field detection section A consists of a polarizer 3, a Faraday rotation element 4, and an optical prism 7, and uses the vibration direction of the light of the polarizer 3 (direction of linearly polarized light) and the optical principal axis of the optical prism to connect the optical fiber 2-2. photodetector 6-1.6-2 respectively through
Detect with. Here, the optical prism used is such that the intensities P+ and Pa of the detected light are expressed by the following equations.
・・・・・・・・・・・・ （３）
これを演算回路で
なる計算を行えば、式＜３） 、 （４）より５＝ｓｉ
ｎＦ＝ｓｉｎ（Ｖ、ＨＬ） ”−””−”−”’・（
５）となる。式（５）は光源の強さ、伝送効率に無関係
で、ただ磁界に比例する出力を与える。このため検出出
力は非常に安定である。・・・・・・・・・・・・ (3) If this is calculated using an arithmetic circuit, then from formula < 3), (4), 5=si
nF=sin(V,HL) ”−””−”−”'・(
5). Equation (5) is independent of the strength of the light source and the transmission efficiency, and gives an output that is proportional to the magnetic field. Therefore, the detection output is very stable.
以下、本発明を実施例を参照して詳細に説明する。Hereinafter, the present invention will be explained in detail with reference to Examples.
実施例
光源としては出力（Ｐｏｕｔ）が６０ｍＷの発光ダイオ
ードを用い、光ファイバとしては直径６００μｍの石英
ファイバをコアとし１００μｍ厚のプラスチックのクラ
ツディングをもつものを使用した。光源の波長は０．８
μｍであつ九。ファラデー回転素子としては、（ＹＳｍ
ＬｕＣａ）ｓ （ＦｅＱｅ）ｓＯＩｌなる厚み１５μ
ｍの磁性ガーネット薄膜を厚み０．３５■のガドリニウ
ム・ガリウム・ガーネットＧｄ５ＧａｉＯ＋＊の両面に
、磁化方向が上記面に垂直となるように液相成長法によ
って形成したものを用いた。光学プリズムとしては大き
さが５×５謹で長さが約１２簡のウォラストンプリズム
であり、二つの光の分離角は約２０度であった。第２図
における光ファイバ２−１と偏光子３の間に直径１．８
■の棒レンズを入れ、光ファイバ２−１よりの光を平行
にした。また光ファイバ２−２とウォラストンプリズム
の間にも結合効率を上げるため同一の棒レンズを用いた
。A light emitting diode with an output (Pout) of 60 mW was used as the light source of the embodiment, and an optical fiber having a core of a quartz fiber with a diameter of 600 μm and a plastic cladding of 100 μm thick was used as the optical fiber. The wavelength of the light source is 0.8
Nine in μm. As a Faraday rotation element, (YSm
LuCa)s(FeQe)sOIl thickness 15μ
A magnetic garnet thin film having a thickness of 0.35 mm was formed on both sides of a gadolinium-gallium-garnet Gd5GaiO+* having a thickness of 0.35 cm by liquid phase growth so that the magnetization direction was perpendicular to the above-mentioned planes. The optical prism was a Wollaston prism with a size of 5 x 5 and a length of about 12 lenses, and the angle of separation of the two lights was about 20 degrees. The diameter between the optical fiber 2-1 and the polarizer 3 in Fig. 2 is 1.8 mm.
A rod lens (2) was inserted to make the light from the optical fiber 2-1 parallel. Further, the same rod lens was used between the optical fiber 2-2 and the Wollaston prism in order to increase the coupling efficiency.
光検出器としてはＰＩＮフォトダイオードを用いそれぞ
れの出力を検出し、式（４）の演算を行わせた所第３図
に示すように良好な出力が直線性よく得られた。As a photodetector, a PIN photodiode was used to detect each output, and when the calculation of equation (4) was performed, a good output with good linearity was obtained as shown in FIG.
第１図は従来の光ファイバを用いた磁界検出器の構成図
で、第２図は本発明における磁界検出器の構成図である
。第３図は実施例の説明図で、出力と磁界の強さの関係
を示す。
１・・・光源、２−１．２−２・・・光ファイバ、３・
・・偏光子、４・・・ファラデー回転素子、５・・・検
光子、６゜６−１．６−２・・・光検出器、７・・・光
学プリズム。
代理人 弁理士 薄田利幸
罫 １ 図
４
−２
第３図
伍昇Ｑ 狼−２＜４”ラスジFIG. 1 is a block diagram of a conventional magnetic field detector using an optical fiber, and FIG. 2 is a block diagram of a magnetic field detector according to the present invention. FIG. 3 is an explanatory diagram of the embodiment, showing the relationship between the output and the strength of the magnetic field. 1... Light source, 2-1.2-2... Optical fiber, 3.
... Polarizer, 4... Faraday rotation element, 5... Analyzer, 6°6-1.6-2... Photodetector, 7... Optical prism. Agent Patent Attorney Toshiyuki Usuda 1 Figure 4-2 Figure 3 Gosho Q Wolf-2 < 4” Rasuji
Claims (1)
磁界検出部と、上記検出部からの光を計測する計測部と
上記光源と検出部および計測部を光学的に結合する光伝
送路とからなる磁界測定装置において上記検出部が偏光
子、ファラデー回転能を有する媒質と光学プリズムで構
成されたことを特徴とする磁界検出器。 ２、特許請求の範囲第１項記載の磁界検出器において、
光学プリズムは、入射光″ｌｒ、２つの直線偏光の光に
分離するプリズムで構成されている磁界検出器。 ３．４Ｇ許請求の範囲第１項記載の磁界検出器において
、分離された２つの光を、実質的に２本の光ファイバで
計測部まで導びき、それらの出力の差と和の比を取って
計測する磁界検出器。[Claims] 1. A magnetic field detection section comprising a light source and a medium having Faraday rotation ability, a measurement section that measures light from the detection section, and an optical system that connects the light source, the detection section, and the measurement section. What is claimed is: 1. A magnetic field detector comprising a magnetic field measuring device comprising a coupled optical transmission path, wherein the detecting section comprises a polarizer, a medium having Faraday rotation ability, and an optical prism. 2. In the magnetic field detector according to claim 1,
The optical prism is a magnetic field detector composed of a prism that separates the incident light "lr" into two linearly polarized lights. A magnetic field detector that essentially guides light through two optical fibers to a measuring section and measures the difference and sum of their outputs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12518381A JPS5827071A (en) | 1981-08-12 | 1981-08-12 | Photomagnetic field detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12518381A JPS5827071A (en) | 1981-08-12 | 1981-08-12 | Photomagnetic field detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS5827071A true JPS5827071A (en) | 1983-02-17 |
Family
ID=14903951
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12518381A Pending JPS5827071A (en) | 1981-08-12 | 1981-08-12 | Photomagnetic field detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5827071A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60138480A (en) * | 1983-12-27 | 1985-07-23 | Hitachi Cable Ltd | Optical magnetic field sensor |
| JPS6126875A (en) * | 1984-07-17 | 1986-02-06 | Toshiba Corp | Measuring device for magnetic field |
| JPS62133973A (en) * | 1985-12-05 | 1987-06-17 | 松下電器産業株式会社 | Disposal apparatus |
| US4896103A (en) * | 1985-06-29 | 1990-01-23 | Kabushiki Kaisha Toshiba | Current measuring magnetic field sensor having magnetooptic element with its easy axis of magnetization at right angles to the magnetic field generated by the current |
| US4956607A (en) * | 1988-03-03 | 1990-09-11 | Ngk Insulators, Ltd. | Method and apparatus for optically measuring electric current and/or magnetic field |
-
1981
- 1981-08-12 JP JP12518381A patent/JPS5827071A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60138480A (en) * | 1983-12-27 | 1985-07-23 | Hitachi Cable Ltd | Optical magnetic field sensor |
| JPS6126875A (en) * | 1984-07-17 | 1986-02-06 | Toshiba Corp | Measuring device for magnetic field |
| US4896103A (en) * | 1985-06-29 | 1990-01-23 | Kabushiki Kaisha Toshiba | Current measuring magnetic field sensor having magnetooptic element with its easy axis of magnetization at right angles to the magnetic field generated by the current |
| JPS62133973A (en) * | 1985-12-05 | 1987-06-17 | 松下電器産業株式会社 | Disposal apparatus |
| US4956607A (en) * | 1988-03-03 | 1990-09-11 | Ngk Insulators, Ltd. | Method and apparatus for optically measuring electric current and/or magnetic field |
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